Error converting APNG to WEBP

[sjbitcode]

What did you do?

Opened an animated png file and tried saving it as a webp image.

I tried two animated png's:

• without transparency (source)
  
• with transparency (source)
  

What did you expect to happen?

I expected the webp versions to successfully save the animations for both images.

What actually happened?

Error from WebPImagePlugin.py on save:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/sangeeta/Code/python-pillow-practice/venv/lib/python3.10/site-packages/PIL/Image.py", line 2431, in save
    save_handler(self, fp, filename)
  File "/Users/sangeeta/Code/python-pillow-practice/venv/lib/python3.10/site-packages/PIL/WebPImagePlugin.py", line 287, in _save_all
    enc.add(
TypeError: 'float' object cannot be interpreted as an integer

What are your OS, Python and Pillow versions?

• OS: macOS Monterey v12.5
• Python: 3.10.2
• Pillow: 9.4.0

from PIL import Image

# walking man apng
img = Image.open('img/man.png')
print(img.format)
print(img.mode)
print(img.get_format_mimetype())
print(img.info)
img.save('transformed/man.webp', save_all=True)


# beach ball apng
img2 = Image.open('img/beach_ball.png')
print(img2.format)
print(img2.mode)
print(img2.get_format_mimetype())
print(img2.info)
img2.save('transformed/beach_ball.webp', save_all=True)

The output:

>>> img = Image.open('img/man.png')
>>> print(img.format)
PNG
>>> print(img.mode)
RGB
>>> print(img.get_format_mimetype())
image/apng
>>> print(img.info)
{'loop': 0, 'transparency': (0, 0, 16), 'bbox': (0, 0, 1400, 1050), 'duration': 41.666666666666664, 'disposal': 0, 'blend': 0}
>>> img.save('transformed/man.webp', save_all=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/sangeeta/Code/python-pillow-practice/venv/lib/python3.10/site-packages/PIL/Image.py", line 2431, in save
    save_handler(self, fp, filename)
  File "/Users/sangeeta/Code/python-pillow-practice/venv/lib/python3.10/site-packages/PIL/WebPImagePlugin.py", line 287, in _save_all
    enc.add(
TypeError: 'float' object cannot be interpreted as an integer


>>> img2 = Image.open('img/beach_ball.png')
>>> print(img2.format)
PNG
>>> print(img2.mode)
RGBA
>>> print(img2.get_format_mimetype())
image/apng
>>> print(img2.info)
{'loop': 0, 'bbox': (0, 0, 100, 100), 'duration': 75.0, 'disposal': 1, 'blend': 0}
>>> img2.save('transformed/beach_ball.webp', save_all=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/sangeeta/Code/python-pillow-practice/venv/lib/python3.10/site-packages/PIL/Image.py", line 2431, in save
    save_handler(self, fp, filename)
  File "/Users/sangeeta/Code/python-pillow-practice/venv/lib/python3.10/site-packages/PIL/WebPImagePlugin.py", line 287, in _save_all
    enc.add(
TypeError: 'float' object cannot be interpreted as an integer

[radarhere]

The error you are encountering can be resolved by either #6996 or #6977

[sjbitcode]

thanks for the quick reply @radarhere! Looking forward to seeing those changes merged in! 😄

[radarhere]

Oh, actually, if you want an immediate way to fix the error, you could just insert img.info["duration"] = round(img.info["duration"]).

from PIL import Image

# walking man apng
img = Image.open('img/man.png')
print(img.format)
print(img.mode)
print(img.get_format_mimetype())
print(img.info)
img.info["duration"] = round(img.info["duration"])
img.save('transformed/man.webp', save_all=True)


# beach ball apng
img2 = Image.open('img/beach_ball.png')
print(img2.format)
print(img2.mode)
print(img2.get_format_mimetype())
print(img2.info)
img2.info["duration"] = round(img2.info["duration"])
img2.save('transformed/beach_ball.webp', save_all=True)

[sjbitcode]

Thanks @radarhere, that's a clever workaround!

This is probably a separate issue, but the man.webp image has a black background after the first frame; I've attached it here as a zip because I couldn't upload a webp image!
man.webp.zip

I started reading through #5755 and #5837, maybe this is a color palette issue?

[radarhere]

I created PR #7018 to fix that part, applying transparency to the new frame before blending it with the current image.

[sjbitcode]

Just tested this, and it works perfectly! Thanks for the quick fix again!

Will this be included in Pillow 9.5.0?

[hugovk]

Yes, #7018 has been merged and will be in 9.5.0 on 1st April 2023.

Thanks for the report.

[radarhere]

Pillow 9.5.0 has now been released.